Automatic pressure cooker



5 Sheets-Sheet 1 Filgd Nov. 2'7, 1945 INVENTOR. FREDER/CK KORN A T TORNE Y5 July 18, 1950 Filed Nov. 27, 1945 F. KORN AUTOMATIC PRESSURE COOKER 3 Sheets-Sheet 2 INVENTOR. FREDER/CK KORN ATTORNEYS F'atented July 18, 1950 UNITED STATES PATENT OFFICE AUTOMATIC PRESSURE COOKER Frederick Korn, Freeport, N. Y.

Application November 27, 1945, Serial N 0. 631,164

9 Claims. 1

My present invention relates to pressure cookers, and particularly to a pressure cooker designed and constructed to be entirely automatic in its operation.

Also, my invention relates to the pressure cooker which is simplified in construction, re quires no mechanical skill or dexterity on the part of the housewife to operate, and which nev My invention contemplates a pressure cooker having a heating element associated therewith and so arranged that heat transfer from the heating element to the pressure cooker is direct and immediate.

ment of a pressure cooker so that a removable in viating the necessity for cleaning the entire pressure cooker after each cooking operation.

The foregoing and many other objects of my invention will become apparent in the following description and drawings in which:

Figure 1 is a cross-section through my novel pressure cooker showing the various elements thereof.

Figure 2 is a view taken along line 2-2 of Figure 1 looking in the direction of the arrows.

Figure 3 is a schematic view showing my novel electro-rnechanical system for controlling the various operations of my pressure cooker in accordance with predetermined settings of various elements thereof.

Figure 4 is a cross-sectioned view of the exhaust valve used in the cooker.

Figure 5 is a cross-sectioned view of the safety valve also used in the cooker. My invention also contemplates the arrange- Since most pressure cookers are necessarily, 'by I reason of the fact that they must resist internal pressure, relatively heavy or massive structures, it has always been a rather difficult task to cl ean. The utilization of the insert container for the food which is to be cooked obviates this.

My invention lso contemplates the utilization of a removable drip ring in connection with the insert container to insure that steam which is condensed by the cover is returned to the insert container and not to the area between the insert container and the outer wall of the pressure cooker.

Also, my invention contemplates a novel electro-mechanical system responsive to various container associated therewith to obviate the necessity for cleaning the entire pressure cooker after each cooking operation.

A further object of my invention is the provision of a novel drip ring associated with the insert container in order to return steam condensed by the cover to the interior of the insert container.

Another object of my invention is the provision of a novel electro-mechanical control system associated with various elements of the pressure cooker for controlling each of the operations of the pressure cooker in accordance with predetermined settings of various elements thereof.

Figure 6 is a cross-sectioned view of the pressure gauge shown schematically in Figure 3.

Referring first to Figure 1, I have here shown my novel pressure cooker ID as comprising a principal container or housing II and a cover member l2. The principal container or housing has an interior cylindrical wall M defining the interior of the pressure. cooker. Cylindrical Wall 5 1 is provided adjacent its upper end with an annular flange Hi to provide a rest for the cover l2 in the manner hereinafter described.

The cylindrical interior wall 14 also has integrally secured thereto a bottom wall |1-the bottom wall ill and cylindrical wall l4 forming a container open at the top. Wall i4 is extended below the bottom wall I! at the annular flange to form a circular recess 2! between the bottom wall i1 and the base on which the flange '20 rests.

The lower container II also has an outer cylindrical wall 22 which is secured by welding, brazing or otherwise at 23 to the outer edge of the upper annular flange [6. The outer casing or container section 22 has a bottom wall 25 preferably integral therewith.

An asbestos plate 26 is secured to the upper surface of the bottom wall 25 in any suitable manner and the annular flange 20 of the inner container l l-l'l rests thereon, the recess 2| being entirely enclosed by the bottom wall ll of inner container 14, the bottom wall 25, the outer casing 22, and the asbestos sheet 26, as well as by the annular flange 20.

An electrical heating element 35! preferably of a high power quick-heating type is secured in any suitable manner in contact with the underside of the bottom wall I! of the inner wall M, so that a heat transfer between the heating element 30 and the bottom wall H can readily occur. The heat element 3!] is, however, insulated from the bottom wall 25 of the outer casing by the recess 21' and the asbestos plate 26.

The outer casing 22 and the inner wall M are insulated from each other by the space 32, which space may, however, be evacuated or preferably is filled with a suitable fibrous insulation material.

The inner wall [4 is extended'at 33 above its annular flange it to form a plurality of breechblock elements 34 spaced upwardly from the flange it by sufiicient distance to readily receive the matching breech-block elements 36 of the cover 12.

The cover l2 has an inner wall t8 somewhat dome-shaped in form, as shown in'Figure 1, and terminating in the annular flange 4| which carries the breech-block elements 35. The cover 52 also has an outer casing :32 connected at 43 to the outer edge ofthe annular flange ll and spaced from the inner wall Mi.

The space t between inner wall it and outer casing 42 of the cover l'2 may be evacuated for ins'iilationpurposes or preferably is filled with a suitable fibrous insulating material. The cover I 2" is provided with a handle or other suitable means for readily rotating the same in order to engage or disengage the breech-block elements 34 and 36.

Preferably the inner wall ii! of the cover and its associated flange M and breech-block elements 36 as well as the inner wall l of the lower container together with its associated elements including bottom wall H and flanges 20 and It are of cast metal. The outercasings 22 and 42 are preferably of sheetmetal.

The inner wall MB of the cover 52 is provided with an annular recess 53} above the breech-block elements 36 at such a height as to match the upper end id of the container wall M; a gasket 5| is secured in any suitable manner in the recess 58. Internal pressure within the container would drive the gasket 5i into sealing engageinent against the upper end it of the inner Wall Hi.

My novel pressure cooker is provided with an insert container Ell open at the top and closed at the bottom, the insert container cc resting on the bottom wall ll of the interior of the pressure cooker and thus being in eificie-nt heat transfer contact with the bottom wall it so that heat from the heating element 32'! may readily be transferred thereto.

' Suitable means may be provided if desired on the bottom wall ii to space the insert container Whom the inner wall Hi, such means including preferably an annular ridge 62 in the upper surface of the bottom wall ll. For ordinary cooking operations, the water necessary to generate the steam is placed only in the insert container 69 and the food to be cooked in the pressure cooker is also placed in the insert container 60. The insert container 68 is then inserted in the interior of the pressure cooker to rest on the bottom wall I! and the cover is secured in place.

Steam which is generated and which comes into contact with the bottom surface of the cover 40 will to some extent condense and flow back into the pressure cooker. Thus, part of the steam will flow back into the space GI and into contact with the wall it and bottom wall I! of the pressure cooker unless means are provided to prevent such occurrence.

In order, therefore, to guide all of the condensed moisture back into the insert container 60 and thus to prevent moistening of the inner wall M of the principal pressure cooker itself and the consequent necessity for cleaning the same, I have provided a novel drip ring is having an annular flange H and a general funnelshaped cross-section; the Wall of the drip ring 4 ill is partly conical in form, the upper opening 12 of the drip ring being much wider than the lower opening 13 thereof.

As will be seen, the annular flange H of the drip ring 70 rests on the annular ledge 15 provided at the upper end of the inner wall l4 while the drip ring it extends into the insert container 60 and the narrower opening 13 communicates with the insert container 60.

Any moisture resulting from condensation of steam by the cover will thus be guided back to the interior of the insert container 63 and the principal wall of the pressure cooker will not be soiled thereby.

In actually placing the food into the pressure cooker, the cover is'of course first removed, the insert container 643 is placed with the'appro'priate water and food into the interior of the-pressure cooker, the drip ring 10 is then placed in posi; tion as shown, and-the cover I2 is then secured in position.

In order to remove the food, the cover i2 is removed and the drip ring 10 is taken out. The food may then be removed from the insert container Bil or the insert container" 56 may be removed as a whole.

Thus it will be seen that for most purposes, only the insert container 60' need be washed after each cooking. It will also be seen that the drip ring 70 acts as a baster returning the condensed moisture from the cover back to the food in the insert container 60.

When it is desired to steam food, water is placed in the main body" of the pressure cooker itself. A suitable wire-grid or rack, not shown, is placed on the bottom wall ll of the main cooker body and the insert container 60 isplaced on the rack. The drip ring it is in this case not used and steam condensed by the cover 12 flows down the domeshaped interior of the cover It! to the annular ledge IE-and down the sidewall is to be re-vaporized into steam once more. By this means, my novel cooker may be used for combined cooking and steaming of food:

My pressure cooker shown in Figure 1 is provided with various controls, the function of which is hereinafter described in connection with Figure 3. The heating element 3E) has already been re-' ferred to and is connected by suitable means to the other elements'hereinaifter described in connection with Figure 3: u

The cover l?- is provided with an exhaust valve 8!) soarranged as to permit the passage of air therethrough from the interior of the pressure cooker to the exterior. The exhaust valve 8E3 is so-arranged that passage of steam'closes it either by thermostatic action or by the pressure of the steam. Preferably, the internal steam pressure is used to-close the valve.

Figure 4 shows a vertical cross-section through exhaust valve 86; The lower outside portion of valve body 2513 is threaded and screws into inner wall it of cover I The lower inside portion of valve body 2-50 is threaded to accommodate retainer 25! which serves to keep thermostatic conical spiral Z5'2'in'p1ac'e inside valve body 250. Thermostat 252 is of bi me'tallic construction and is so arranged as to expand with rise in temperature. The upper end of thermostat 252 holds the stem of ball van/e253. Normally, valve is open as shown in Figure 4. Passage of steam through valve 80 closes the valve by expanding thermostat 252, seating ball valve 253 against the conical valve seat which forms the upper inside portion of valve body 250.

Thus, when the food in the pressure cooker is first heated, air is driven off through the exhaust valve 80. As the interior begins to fill with steam, air above the steam is driven off more rapidly. When the interior is sufficiently filled with steam to eject steam through the exhaust valve 80, it closes and the pressure cooker begins to operate in the well known manner as a pressure cooker.

My novel pressure cooker is also provided with a pressure gauge 20 connected by the threaded tube SI, threaded into the threaded opening 92 of the wall 5 to the interior of the pressure cooker. The outer casing 22 has a suitable opening for the face of pressure gauge 92.

My novel pressure cooker is also provided with a timing clock 5 id mounted in any suitable manner in the outer casing 22 of the pressure cooker. As hereafter described in connection with Figure 3, it may be set to close a circuit to the heating element at at any time desired after the initial clock setting.

It is also arranged so that it is set to time the cooking operation when the desired pressure is reached in the pressure cooker. When the desired cooking time, measured from the time pressure is obtained in the pressure cooker, has ended, the timing clock l Iii will automatically switch off current to the heating element 38.

My novel pressure cooker is also provided with a safety valve I29 secured in the cover I2 in any suitable manner and arranged to release pressure in the cooker in the event of the failure of automatic pressure control.

Figure 5 shows a vertical cross-section of safety valve I20. The lower outside portion of valve body 254 is threaded and screws into inner wall 40 of cover 82. The upper inside portion of valve body 254 is threaded to accommodate retainer 255 which serves to keep compression spring 256 in place inside valve body 254. Normally, spring 25% holds ball valve 251 seated against the conical valve seat which forms the lower inside portion of valve body 252. However, excessive pressure developed inside the cooker will overcome the pressure orspring and will lift ball valve 251 away from its seat. This will open the valve I28 and allow steam to escape till a safe pressure is again attained inside the cooker.

My novel pressure cooker is also provided with a pressure release valve 53E; connected by the threaded tube ltl in the threaded opening I32 of the wall M to the interior of the pressure cooker. As hereinafter described in connection with Figure 3, the pressure release valve I30 can be set, however, to open automatically at the termination or the cooking period or to require manual release.

Referring now to Figure 3, I have here shown schematically the automatic features of my novel pressure cooker. In the first place, it should be seen that the pressure gauge at is essentially a Bourdon tube 23 which tends to straighten out in accordance with the internal pressure therein.

The outer end 9 of the Bourdon tube 93 is connected to the link 95 which is in turn connected at 92 to the contact arm W, contact arm 91 is pivotally mounted on the pivot 98. Contact plate 99 is also pivotally mounted on the pivot 98 and is provided with a pointer tilt registering with the pressure scale IUI.

Contact plate 92 is provided with a plurality of contacts 582, we, M34, 565 and me which moves with the contact plate 99. The contact plate 99 is pro-set by moving the plate 99 and 6 pointer I00 to the particular pressure desired with respect to the scale IflI.

In Figure 3 the contact plate 99 of the pointer I has been moved to a setting for 15 pounds cooking pressure. Should the setting be made for 10 pounds cooking pressure, then the contact plate 99 and the associated contacts would be shifted clockwise to an appropriate degree-approximately 10 degrees clockwise and all of the operations would then take place at an earlier point or at lower steam pressure and at a smaller expansion of the Eourdon tube.

The timing clock H0 consists essentially of two separate clock or timing mechanisms I I3 and H2. The purpose of clock H3 is to close switch III of relay 258 at a predetermined time. This is accomplished as follows: Slip ring 26I and contact 2659, both insulated from the clock mechanism, and clock pointer 25%} are all driven by the mechanism of clock IIB. Slip ring 263 and contact ring 284, both insulated from the clock mechanism, and indicating pointer 262 all are rotatable as a unit and can be set at any predetermined time. When clock pointer 25?: reaches this predetermined time, contact 260 touches ring 264 allowing current from line 200 to flow through lead 261, brush 265, slip ring 263, contacts 264 and 26b, slip ring 28I, brush 266, lead 268, coil 269 of relay 258 and lead 210 to line 209. The energizing of coil 269 closes switch III of relay 258. The length of contact ring 264 is large enough to permit switch III to remain closed for a period longer than will ever be encountered in normal use of the pressure cooker. When desired, immediate closing of switch III can be accomplished by manually closing switch 213. Clock H3 is electrically driven from lines 201] and 299 through leads 2i! and 212. Clock II3 may also be spring driven, in which case leads 21! and 212 are dispensed with.

The purpose of clock H4 is to open normally closed switch H2 of relay 214 after a predetermined period of time. Clock I I2 is electrically driven from leads 223 and 224 and as hereinafter described is set into operation when cooking pressure is reached. Slip ring 211 and contact 216, both insulated from the clock mechanism, and pointer 215 are all driven as a unit by the mechanism of clock Il l. Pointer 215 is set to the desired period of time. When the clock I I4 is set into operation, pointer 215 rotates counter-clockwise, indicating the amount of time remaining till switch II2 will be opened. When pointer 215 reaches zero, contact 2% reaches contact 219, allowing current from line 203 to flow through lead. 280, contacts 219 and 216, slip ring 211, brush 213, lead 28l, coil 282 Of relay 214 and lead 283 to line 209. The energizing of coil 282 opens normally closed switch l I2 of relay 214. As to be hereinafter described, clock II I also stops at this point.

Figure 3 also shows a spring driven clock 293 which can replace electrically driven clock IM. All parts of clock 291-3, which are the same and perform the same functions as parts of clock I I4, are numbered the same. Clock mechanism 294 is the same as any commercial spring driven stop watch except that it has only one hand which can be set at any place on the dial. The clock mechanism runs only when button 292 is depressed, and stops whenever button 292 is released. As hereinafter described, when the desired pressure is reached in the cooker, conductors 223 and 222 are energized, thus energizing coil 285 of clock 293. This pulls the right hand end of armature 283 upwards against the resistance of tension spring 239. Armature 286 rotates about pivot 23? and depresses button 232, thereby setting clock mechanism 2% into operation. When coil-285 is vde-energized, tension spring 289, attached to armature 236 at point 233 and to clock 294 at point 233, pulls armature 280 back to its original position, thereby releasing button 292 and stopping clock mechanism 294. It is thus obvious, that clock 293, though spring driven, performs exactly the same functions as electrically driven clock I Id.

The .heating element 30 is in series with the normally closed switch H2 and the normally open switch iII so that it will be brought into operation when switch III is closed and so that it will be turned oil when switch II2 is opened.

Valve I3ii is a steam pressure release valve surrounded by the solenoid coil I35. The valve is a ball valve I36 seated in the valve seat I 3'1 and arranged so that it is normally held open by compression spring hit so that steam within the chamber I may escape into the tube I3I and out through the opening I40. The solenoid armature MI in the tube I3! is arranged so that when the coil I35 is energized, the armature I lI will be driven to the right. Armature MI is, however, biased toward the left by compression spring I45 bearing at one end against the face it of armature MI and at the opposite end against the end VII of tube I3I.

Armature Isl is provided with a stud I50 holding the ball valve I36. When the coil I33 is energized, armature I iI is pulled to the right compressing the spring M-5 and driving stud I59 and ball valve I to seal the opening I31 When the coil IE5 is de-energized, the spring M5 drives the armature I II to the left so that the ball valve I36 may be moved out of the valve seat or opening I3? to permit steam to escape.

The armature It! is appropriately slotted or grooved at Hi3 to permit the steam which is rereleased to by-pass the armature and escape through opening Hi0. Armature I ll and hence the valve I 33 may be locked in valve closing posi- I tion by the nut H53 threaded on the threaded end I5! of tube I3i and having the central stud I32. I

When the nut I630 is turned in, stud I02 bears against the face I35 of armature I driving it to the right and thus driving its pin or stud I and ball valve I33 to close the same. This overcomes the action of compression spring M5 and maintains the valve structure i to closed irrespective of energization or de-energization of the solenoid coil I35.

Thus, for automatic release of steam pressure at a predetermined time, nut I69 is maintained in its outermost or retracted position so that the valve may be opened or closed in response to oleenergization or energization of the solenoid coil I35. When the nut I is turned in, then the valve structure I30 will remain closed whether or not solenoid coil I35 is energized or de-energized.

Tracing now the operation of the device as shown, the contact arm 9! is normally in a position where its end engages contact stud I02. Switch I l I is open and switch IIZ is closed. Clock II3 is set to close the switch III at a predetermined time and clock H4 is set to open the switch II2 at a predetermined time. Thus, for instance, should the housewife desire to pressure cook a pound Of meat for 25 minutes, starting at 11:35, she will set the point 262 of clock I I3 at 11:35. Assuming that the pound of meat will take 25 minutes to cook at 15 pounds pressure,

8 she will set the pointer 215 of clock H4 at 25 minutes. since 15 pounds pressure is desired for the cooking operation, the pointer I00 is set oppesite the 15 pound mark on scale IOI. Again at the initiation of all of these operations, contact arm Q'I is at the contact I02.

.At 11:35 in the example above described, switch III is closed and a circuit is then established from line 200 to the switch I II to the conductor 2M to the closed switch I I2 through the conductor 202 to the section 28 of heating element 30; then through conductor 20A to the contact stud I02, then through contact arm 9? to the conductor 206 and through this conductor to the solenoid coil I35; then through conductor 208 to the opposite side of the circuit through line 200.

The heating element section 284 is thus energized and begins to heat the water and food within the container 32. The solenoid coil I35 of valve structure I33 is energized to attract the armature I 'iI to the right to drive ball valve I36 against the valve seat l3? and to close the valve structure I33 so that steam cannot escape through the valve structure I30.

Contact arm QI is sufficiently wide at its contact end so that it will bridge adjacent contacts m2 and I03 as it passes thereacross. As the temperature rises, the water in the container 60 is vaporized into steam and the air at the top of the pressure cooker is driven off through the valve 80.

When steam begins to escape through the valve 30, the valve is closed and now pressure begins to rise in the interior of the pressure cooker. This is so because valve structure I30 was closed on energization of solenoid coil I35 and valve 80 was closed on the escape of steam therethrough and there are no other valves except the safety valve I20.

As pressure rises, the end of contact arm 91 is driven by the Bourdon tube 33 along the contact stud K02 and on to the contact stud I03. This is so because, as the end S4 of the Bourdon tube 93 is driven to the left by expansion thereof in response to steam pressure, lirlc 35 is forced up thus causing the contact arm 91 to rotate counterclockwise around its pivot 38. When the end of contact arm 07 has left the contact stud I02 and has engaged contact stud I03, resistance 2I5 is inserted in series with the section 284 heating coil 30. This lowers the current through the heating element 3B and reduces its heat output. The insertion of resistance 2H5 prevents overshooting of the desired pressure.

The circuit now is from line 200 through switch III, conductor 25H, switch H2, conductor 202, resistance 28 i, resistance 2I5, conductor 2I'I, contact I333, contact arm 9?, conductor 206, solenoid coil I35 and conductor 20?. back to the opposite side of the circuit 209.

As the contact arm 91 is now moved further upwardly or counterclockwise around the pivot 98 on further expansion of the Bourdon tube 93, it leaves the contact stud I 73 and engages contact stud I04. At this time resistance 220 is inserted in series with resistance 2I5 and resistance 284. This reduces the current through the heating element 30 to the value necessary to maintain constant pressure and at this point, it will be seen the contact arm 3'I has moved into registry with the pointer I00 which has been set at the predetermined pressure.

The circuit now is again from line 200 through switches I I! and II 2, resistance 284, resistance 2I5, resistance 220, conductor 222, contact stud I04, then through the contact arm 91, conductor 9 206, solenoid coil I35, conductor 208 andback to the opposite side of the circuit 209.

Also, as contact arm 9'! moves into registry with pointer I00, the former engages contact I06 and a circuit is established from line 200 through switches III and H2, conductors 202 and 224, timing clock I I4, conductor 223, contact stud I06, arm 91, conductor 20E, solenoid coil I35, conductor 208, and back to the opposite line 209.

Thus, when the desired pressure is reached, the clock H4 is energized for operation and now begins to time the cooking operation. It will thus be seen that the operation of the timing device H4 is initiated only when proper cooking pressure is reached.

Also it will be seen, that should the pressure within the cooker at any time fall below that required, arm 97 will leave engagement with con tact I06 and clock IM will cease operation and will not start again until, the required pressure has been re-established. However, should the pressure rise above the required value, arm 91 will maintain engagement with contact I06, and timing will not be interrupted.

At the end of the 25 minutes previously assumed, timing device II4 will open switch II2 which will de-energize heating coil 30 and will also de-energize the solenoid coil I35 in series therewith. Also, since the circuit for timing clock IM includes switch N2, the clock will stop rotation when the latter switch is opened.

Should the heat and, therefore, the pressure continue to rise beyond the pre-set pressure (15 pounds in the example shown) then the contact arm 91 is moved upwardly by further expansion of the Bourdon tube 93 into engagement with contact stud I05. This inserts additional resistance 230 in series with resistances 220, U and 2.84, reduces the current therethrough, and lowers the heat output thereof.

The circuit now is from line 200 through switches III and H2 to resistances 284, 2I5, 220 and 230 to the conductor 232 to contact stud I05, contact arm lll, conductor 20% to coil I35 to conductor 20B and to the opposite side 209 of the circuit.

The insertion of this additional resistance lowering the heat output and thus lowering the temperature should result in reduction of pressure within the pressure cooker so that the Bourdon tube 93 may contract and conductor 97 be returned to contact stud I04, at which time resistance 230 will be cut out and the heat output of heating element 35! he stepped up to proper cooking temperature.

Thus, resistances 2B0, 2I5 and 22!} should be so matched that the output will result in proper cooking temperature continuously throughout the cooking cycle. Should the contents of the cooker, however, be such as to permit excessive rise in temperature and therefore of pressure, the intr0- duction of resistance 230 lowers the output. Should this rise in temperature and therefore in pressure proceed beyond reasonable bounds, then the further expansion of Bourdon tube 03 moves the contact arm ii? further counterclockwise on? the stud 105.

At this point, it will be obvious that the circuit to heating element 30 is broken. The heating element 30 is deenergized and the coil I35 is deenergized, thus opening valve I30 and permitting release of pressure to relieve the internal pressure condition within the cooker. This will immediately result in contraction of the Bourdon tube 93 until the contact arm 91 once more engages contact stud I05.

At this time, heating element 30 will be energized and the coil I35 will be energized once more. Valve I30 is thus closed and the heating element begins to operate once more to maintain pressure. Since resistances 284, 2I5, 220 and 230 are in series therewith, the output of the heating element 30 will be relatively low and the contact arm 97 should move back to stud I0 3 cutting out resistance 230 so that the output of the heating element 30 will be stepped up slightly to maintain cooking pressure.

In ordinary cases, contact arm 91 will be moved to contact stud Kid and will remain thereat with resistances 284, 2I5 and 220 and coil I35 in series with each other. Only in rare cases will the contact arm 91 move up to stud I05 to be in the additional resistance 23%, and only in extreme cases will it be necessary for the contact arm 91 to move upwardly off the contact stud I05 and off the stud let to break the circuit and turn oh" the heating element and release steam.

Thus, this breaking of the circuit and auto- I matic release of steam through the valve structure I39 when excess pressure is reached, is a complement to the safety feature of the escape or safety valve l20. On excess pressure, the contact arm 91 should move off the stud I06 and turn ofi the heat and release steam through the valve I30 before safety valve I operates.

Safety valve I20 will, however, operate should any of the foregoing elements fail to function for some reason, or should the nut I60 of the valve structure I30 be turned in to maintain steam.

On completion of the 25 minute cooking cycle previously assumed, the clock or time delay device H4 opens switch H2. Since this switch is in series with heating element and coil I35, it de-energizes both of these units so that the heating element 30 is turned off and the solenoid armature I4I moves to the left. This opens the valve structure I30 as previously described and permits the steam in the pressure cooker to escape so that the cover I2 may be removed immediately. Should it be necessary or desirable that the pressure cooker cool down slowly after completion of the cooking cycle, or that the steam within the pressure cooker be condensed into moisture once more within the pressure cooker at the completion of the cooking cycle, then prior to the initiation of the cooking operation the house wife should turn the nut I00 in until the ball valve I33 is locked against the valve seat I3'I as previously described.

The nut I may be turned in at any time during the cooking cycle or just before the timing device H4 completes its pre-set cycle; although in usual cases where it is desired to prevent escape of steam and to cause a slow cooling of the pressure cooker, the nut I80 will be turned in before the cooking cycle begins.

Thus, my novel pressure cooker is entirely automatic in operation and need not be attended in any way. All of the operations preparatory to cooking may be done at any convenient time with the clocks H3 and HG pre-set for desired intervals and the pointer I00 pre-set for the desired cooking pressure. The housewife or other user Of the pressure cooker need merely place the food in the container 60, place the insert container in the pressure cooker, place the drip ring It in position on the ledge lI and secure the cover I 2 to the pressure cooker.

The clock H3 is set for the particular time at '11 which the cooking cycle is intended to begin. The clock H4 is set for the cooking interval. Pointer lei! is set for the cooking pressure; and then the pressure cooker need not further be attended until, the time comes for removal of the cooked contents. Thus, it will be seen that all of the operations are entirely automatic and fool-proof.

It will be obvious that many modifications and variations of my invention will be apparent to those skilled in the art. Thus, the drip ring H! may in appropriate cases be made a part of the cover structure l2 so that a separate operation with respect thereto will not be necessary.

The. various elements of the automatic system may also be modified in obvious ways. Thus, any type of pressure gauge may be used which will move the contact arm 91 in response to the pressure and any type of contact arrangement may be used on the contact plate .99.

Figure 6 shows a preferred arrangement of pressure gauge 9!! in greater detail than shown in Figure 3. All identical parts are numbered the same in both figures. Figure 6 shows a sectional view, greatly enlarged, as would be seen when looking in a downward direction at the pressure gauge shown in Figure 3. The gauge casing 38!] has a threaded hole 3 3i into which isscrewed threaded tube 9!. The other end of tubes! is screwed into threaded hole 92 of wall l4. Thus, tube 9! acts as a mounting for the pressure gauge .98. Bourdon tube 93- is sweatsoldered into hole 3% which has access to the interior of the pressure cooker through holes 382,- 30! and tube 9!. End 94 of Bourdon tube 93 actuates link 95 which in turn actuates arm 3914 through pin 96. Arm MM is fastened by pin 305 to shaft 306 which is free to rotate in bear ing holes 381 in casing 3%. Thus, shaft 305 is rotated by deformation of the Bourdon tube 93 caused by pressure changes within the cooker. Hubs 398 and 310 are fastened by pins 399 and 3 respectively to shaft 305. Hub 3.98 is made of insulating material and carries contact arm 9?. Hub 3!!! carries pointer I'll-2 which indicates the pressure inside the cooker against scale or dial Hl l fitted into recess 333 of casing 3133. Hub 3M is free to rotate on shaft 305. Gear .3 i5 is fastened to hub 3M and meshes with pinion 3| 5. Turning knob 3l8 turns pinion 316 through shaft 3|! which is free to rotate in hole 3H9 of casing Sill]. This turns gear 3l5, adjusting the angular position of hub 3M. Fastened to hub SM is contact plate 99, made of insulating material. Contact plate 99 carries contacts I02, W3, W4, Ilia and I06 which are engaged by contact arm 91. Also fastened to hub 3M is pointer act which indicates against dial It the desired pressure to which contact plate 99 has been adjusted by knob Sit. Dial ill! and pointers H10 and M2 are protected by dial glass 32.0 which fits into recess 32! of casing 386. Glass 3.29 is held in place by bezel 322 which is pressed over edge 323 of casing 360. Outer casing 22 has a suitable opening 324 for the casing 300. However, it is to be noted that the gauge is not supported by wall 22 but only by tube 9! supported in turn by wall I l.

The steam release valve I39 may in certain cases be dispensed with where the pressure cooker is designed so that the steam will always be retained at the end of the cooking cycle. The utilization of the release valve structure I30, however, incorporates an additional safety feature and also provides for selective operation by the user who can determine for herself Whether at should be released or retained.

My novel pressure cooker may also be arranged by placing an appropriate switch 213 between conductors 26'! and 268 so that the heating ele ment 38 may be immediately energized by manually closing switch 213. Also, in this case, by simply setting the clock M4 for a time interval much longer than the desired cooking cycle, the switch 273 may be utilized to control the entire cooking cycle manually when attended operation is desired.

Since many other variations and modifications of my invention should now be obvious to those skilled in the art, I prefer to be bound not by the specific disclosures herein contained but only by the appended claims.

I claim:

.1. An automatic pressure cooker comprising a casing having bottom and side walls and an open top; a pressure tight cover for the open top; an electrical heating element supported in said casa control for said electrical heating element supported in said casing and accessible for adjustment from the outside of said casing, said control comprising a pressure responsive member connected to the interior of said casing and movable in response to variations in pressure within said casing, and a plurality of electrical resistance elements; means for connecting selected resistance elements in circuit with each other and with said heating element in accordance with variations in pressure within the casing; said means including a contact arm connected to and movable by said pressure responsive member; a contact carrying plate having a plurality of contact members successively engageable by said contact arm to connect successive resistances in series with said heating element; a pressure re-- lease valve in said casing; and means for biasin said valve to open position; solenoid means in circuit with said heating element for holding said valve closed; said biasing means being effective to open said valve on de-energization of said heating element and solenoid.

2. An automatic pressure cooker comprising a casinghaving bottom and side walls and an open top; a pressure tight cover for the open top; an electrical heating element supported in said casing; and a control for said electrical heating element supported in said casing and accessible for adjustment from the outside of said casing, said control being responsive to variations in pressure within said casing; and a pressure release valve in said casing; means for biasing said valve to open position; solenoid means energized simultaneously with said heating element for holding said valve closed; said biasing means being effective to open said valve on de-energization oi said heating element and solenoid.

3. An automatic pressure cooker comprising a casing having bottom and side walls and an open top; a pressure tight cover for the open top; an electrical heating element supported in said casing; a control for said electrical heating element supported in said casing and accessible for adjustment from the outside of said casing, said control comprising a pressure responsive member connected to the interior of said casing and movable in response to variations in pressure within said casing, and a plurality of electrical resistance elements; means for connecting se-' lected resistance elements with each other and with said heating element in accordance with variations in pressure within the casing; said means including a contact arm connected to and movable by said pressure responsive member; a contact carrying plate having a plurality of contact members successively engageable by said contact arm to connect successive resistances with said heating element; a pressure release valve in said casing; and means for biasing said valve to open position; solenoid means energized simultaneously with said. heating element for holding said valve closed; said biasing means being effective to open said valve on de-energization of said heating element and solenoid; and additional means for selectively maintaining said valve closed against said biasing means irrespective of the energization and de-energization of said solenoid means.

4. A pressure cooker comprising a casing having bottom and side walls and an open top; a pressure tight cover for the open top; said casing comprising an outer shell and an inner metallic shell; means spacing the inner shell from the outer shell at the bottom and side walls; and a heat insulating filler between the outer and inner shells; an electrical heating element in the bottom wall between the outer and inner shell in heat transferring relation with the inner shell; an inner removable container for said inner shell of the casing; an annular frustro-conical drip ring for said inner shell of said casing; the upper opening of said drip ring being larger than the lower opening; means at the upper end of the inner shell of said casing above the inner container for mounting said drip ring; the lower opening of said drip ring being smaller in diameter than the diameter of the inner container; the drip ring returning moisture condensed on the interior of the cover of the casing to the inner container.

5. A pressure cooker comprising a casing having bottom and side walls and an open top; a pressure tight cover for the open top; said casing comprising an outer shell and an inner metallic shell; means spacing the inner shell from the outer shell at the bottom and side walls; and a heat insulating filler between the outer and inner shells; an electrical heating element in the bot tom wall between the outer and inner shell in heat transferring relation with the inner shell; an inner removable container for said inner shell of the casing; an annular frustro-conical removable drip ring for said inner shell of said casing; the upper opening of said drip ring being larger than the lower opening; an annular ledge at the upper end of the inner shell of said casing above the inner container for mounting said drip ring; the lower opening of said drip ring being smaller in diameter than the diameter of the inner container; the drip ring returning moisture condensed on the interior of the cover of the casing to the inner container.

6. A cooking utensil comprising a casing having bottom and side walls and an open top; a cover for the open top; an inner removable container for said casing; means in the interior of the casing for spacing said inner removable container from the interior side wall of the casing; an annular frustro-conical drip ring for said interior of said casing; the upper opening of said drip ring being larger than the lower opening; means at the upper end of the interior of said casing above the inner container for mounting said drip ring; the lower opening of said drip ring being smaller in diameter than the diameter of the inner container; the drip ring returning moisture condensed on the interior of the cover of the casing to the inner container.

7. A cooking utensil comprising a casing having bottom and side walls and an open top; a cover for the open top; an inner removable container for said casing; means in the interior of the casing for spacing said inner removable container from the interior side wall of the casing; an annular frustro-conical removable drip ring for said interior of said casing; the upper opening of said drip ring being larger than the lower opening; an annular ledge at the upper end of the interior of aid casing above the inner container for mounting said drip ring; the lower opening of said drip ring being smaller in diameter than the diameter of the inner container; the drip ring returning moisture condensed on the interior of the cover of the casing to the inner container.

8. An automatic pressure cooker comprising a casing having bottom and side walls and an open top; a pressure tight cover for the open top; an electrical heating element supported in said casing; and a control for said electrical heating element supported in said casing and accessible for adjustment from the outside of said casing, said control being responsive to variations in pressure within said casing, and a pressure release valve in said casing; means for biasing said valve to open position; solenoid means energized simultaneously with said heating element for holding said valve closed; said biasing means being efiective to open said valve on de-energization of said heating element and solenoid; and adjustable timing means carried by said casing, said timing means being operable to connect said heating element to a source of current at a selected time, to initiate an interval timing operation when a predetermined temperature has been reached within the casing and to disconnect said heating element at the end of a selected interval.

9. An automatic pressure cooker comprising a casing having bottom and side walls and an open top; a pressure tight cover for the open top; an electrical heating element supported in said casing; and a control for said electrical heating element supported in said casing and accessible for adjustment from the outside of said casing, said control being responsive to variations in temperature within said casing, a plurality of electrical resistance elements; a contact member movable by said control member to connect said resistances successively in circuit with said heating element, and a pressure release valve in said casing; means for biasing said valve to open position; solenoid means energized simultaneously with said heating element for holding said valve closed; said biasing means being effective to open said valve on de-energization of said heating element and solenoid.

FREDERICK KORN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,381,282 lark June 14, 1921 1,391,863 Spangler Sept. 27, 1921 1,422,348 Dun-can July 11, 1922 1,702,089 Rohne Feb. 12, 1929 1,931,190 Goughnour Oct. 17, 1933 1,946,220 Lotz Feb. 6, 1934 2,119,455 De Ayala May 31, 1938 2,308,603 Graham Jan. 19, 1943 2,369,932 Allen Feb. 20, 1945 

